Evaluation of Long-Term Gas Hydrate Production Testing Locations on the Alaska North Slope

Abstract

Abstract The results of short duration formation tests in northern Alaska and Canada have further documented the energy resource potential of gas hydrates and justified the need for long-term gas hydrate production testing. Additional data acquisition and long-term production testing could improve the understanding of the response of naturally-occurring gas hydrate to depressurization-induced or thermal-, chemical-, and/or mechanical-stimulated dissociation of gas hydrate into producible gas. The Eileen gas hydrate accumulation located in the Greater Prudhoe Bay area in northern Alaska has become a focal point for gas hydrate geologic and production studies. BP Exploration (Alaska) Incorporated and ConocoPhillips have each established research partnerships with U.S. Department of Energy to assess the production potential of gas hydrates in northern Alaska. A critical goal of these efforts is to identify the most suitable site for production testing. A total of seven potential locations in the Prudhoe Bay, Kuparuk, and Milne Point production units were identified and assessed relative to their suitability as a long-term gas hydrate production test site. The test site assessment criteria included the analysis of the geologic risk associated with encountering reservoirs for gas hydrate testing. The site selection process also dealt with the assessment of the operational/logistical risk associated with each of the potential test sites. From this review, a site in the Prudhoe Bay production unit was determined to be the best location for extended gas hydrate production testing. The work presented in this report identifies the key features of the potential test site in the Greater Prudhoe Bay area, and provides new information on the nature of gas hydrate occurrence and potential impact of production testing on existing infrastructure at the most favorable sites. These data were obtained from well log analysis, geological correlation and mapping, and numerical simulation. Introduction Since the establishment of the Methane Hydrate Research and Development Act in 2000 (Allison and Boswell, 2009), a primary goal of the U.S. national gas hydrate research program has been the determination of the viability of gas production from gas hydrate reservoirs. Today, a wealth of data gathered in the lab, during field tests, and in numerical simulation studies indicates that gas is technically recoverable from gas hydrates hosted in porous and permeable (sand or sandstone) reservoirs using existing technologies (Collett et al., 2009). However, what is not well understood is how long it might take to recover those volumes, from how many wells, with what water production, and what wellbore completion technologies will be required. A program of extended term field tests is needed to address these issues and move toward a better understanding of the economics of natural gas production from gas hydrates reservoirs. To be most effective, this program should feature a series of tests, utilizing different approaches, and applied over a range of geologic settings.